问题：

有时在开发中想直接写一个java文件来测试一些东西，但是AndroidStudio执行的时候会报错。

代码信息：

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("HelloWorld");
    }
}

报错信息

12:04:41: Executing task 'HelloWorld.main()'...

Executing tasks: [HelloWorld.main()] in project D:\AndroidStudioProjects\MyApplication8


> Configure project :app
WARNING: The following project options are deprecated and have been removed: 
android.enableAapt2
This property has no effect, AAPT2 is now always used.



FAILURE: Build failed with an exception.

* Where:
Initialization script 'C:\Users\cj\AppData\Local\Temp\HelloWorld_main__.gradle' line: 20

* What went wrong:
A problem occurred configuring project ':app'.
> Could not create task ':app:HelloWorld.main()'.
   > SourceSet with name 'main' not found.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

Deprecated Gradle features were used in this build, making it incompatible with Gradle 6.0.
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/5.6.4/userguide/command_line_interface.html#sec:command_line_warnings

BUILD FAILED in 116ms
12:04:41: Task execution finished 'HelloWorld.main()'.

解决方案

在.idea文件夹中找到gradle.xml， 打开文件，在<GradleProjectSettings>标签下添加

<option name="delegatedBuild" value="false" />

添加后文件内容

<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
  <component name="GradleMigrationSettings" migrationVersion="1" />
  <component name="GradleSettings">
    <option name="linkedExternalProjectsSettings">
      <GradleProjectSettings>
        <option name="delegatedBuild" value="false" />
        <option name="testRunner" value="PLATFORM" />
        <option name="distributionType" value="DEFAULT_WRAPPED" />
        <option name="externalProjectPath" value="$PROJECT_DIR$" />
        <option name="modules">
          <set>
            <option value="$PROJECT_DIR$" />
            <option value="$PROJECT_DIR$/app" />
          </set>
        </option>
        <option name="resolveModulePerSourceSet" value="false" />
      </GradleProjectSettings>
    </option>
  </component>
</project>

结果

image.png

总结

再次运行就可以显示执行结果了，据说这句话的意思是不让gradle接管构建任务，防止当作gradle的task来执行。